This invention relates to a tamper-proof locking mechanism to be used in connection with access openings of electrical or mechanical device housings. In particular, this invention relates to a versatile, tamper-proof locking mechanism for preventing unauthorized recharging of postage meters.
Postage meters are used by businesses in many countries to dispense postage in lieu of physically purchasing and applying postage stamps. Postage meters are usually attached to a separate postage meter base which has a feed mechanism that feeds letters between the printhead of the postage meter and the meter base. Mechanical postage meters account for the amount of postage remaining in the meter by means of a mechanical descending register. Electronic postage meters account for the remaining postage amount by means of microprocessors and registers stored in memory. Both mechanical and electronic postage meters print the postage value either on a label which is subsequently attached to an envelope, or directly on the envelope. When the postage value remaining in the postage meter is less than a predetermined value, the meter will cease to print. When the available postage is low, then, the postage meter can be returned to the post office, and a post office employee can add a desired postage amount to "reset" meter.
In order to prevent unauthorized access to the interior of the postage meter housing, many countries require the postage meters to be equipped with security locks or sealing mechanisms. Several types of postal-locks or seals have been devised, but none has been universally adopted. In the United States, the access mechanism of the postage meters is usually sealed with a wire and lead seal after a desired mount of postage has been added to the meter. The wire must be cut before one can access the interior of the postage meter housing, or activate a switch that allows one to add postage to the meter. For convenience, this wire and lead seal combination is often referred to herein only as a "lead seal." Other types of postal-lock mechanisms for postage meters utilized in various countries include a tamper-indicating frangible membrane in the form of a paper seal that must be broken to reset the meter, a key lock, a combination of a paper seal and a lead seal, and a combination of a key lock and a lead seal.
Because the required postage meter security mechanisms differ from one country to the next, postage meter manufacturers have had to produce multiple versions of a postage meter, each version having the appropriate postal-lock mechanism for a designated country. Accordingly, many parts of a postage meter are not interchangeable among different versions of the meter. As a result, the price of a postage meter and the repair costs are increased due to the increased number of required parts to be manufactured and kept in inventory.
Conventional postage meters are usually constructed such that the meter housing is secured to the meter chassis by means of a locking mechanism separate from the postal-lock mechanism. This type of construction has resulted in three problems: a) one cannot readily ascertain whether the meter housing is securely attached to the meter chassis without carefully examining the entire meter assembly; b) the number of required parts for the meter is increased; and c) once a meter component is replaced, the entire meter assembly must be realigned so that all of the component parts are in correct relationship to one another.
There is thus a need for a versatile postal-lock mechanism that can readily satisfy the existing postage meter security requirements of various countries and simplify the overall construction of the postage meter by means of combining the postal-lock mechanism with the locking mechanism securing the meter housing to the meter chassis.